In recent days, a solar cell directly converting solar energy to electric energy has increasingly been expected to serve as a next-generation energy source in particular from a viewpoint of global environmental issues. Among various types of solar cells such as a solar cell using a compound semiconductor or an organic material, a solar cell using silicon crystal is mainly employed these days.
In order to improve photoelectric conversion efficiency in a solar cell, an electrode structure in which an area for a light-receiving surface electrode is minimized and series resistance is suppressed has conventionally been proposed. For example, Japanese Patent Laying-Open No. 62-156881 discloses a solar cell shown in FIG. 5. This solar cell is manufactured in the following manner. A light-receiving surface electrode pattern consisting of a main electrode 51 and a grid electrode 52 is formed on an antireflection coating 54 on a silicon substrate 53 by screen printing, followed by heat treatment at approximately 700° C. Accordingly, a silver paste for forming a grid electrode penetrates antireflection coating 54, and the grid electrode is connected to the main electrode. Such a solar cell attains excellent electric contact with silicon substrate 53.
On the other hand, in the conventional solar cell, a ratio of the light-receiving surface electrode pattern to a light-receiving area is as high as approximately 10%. Accordingly, the light-receiving area contributing to power generation is reduced, and surface recombination velocity at main electrode 51 and grid electrode 52 is large, resulting in poorer electric characteristics of the solar cell, in particular lower open-circuit voltage. Though it is possible to increase the light-receiving area contributing to power generation by reducing the electrode area with respect to the light-receiving area by approximately 5% as well as to reduce the surface recombination velocity for raising the open-circuit voltage, series resistance is disadvantageously increased. Then, a fill factor of the solar cell becomes smaller, and obtained electric power is reduced.